Interferons are a family of highly homologous proteins that inhibit viral replication, inhibit cellular proliferation and modulate immune response. Human interferons are grouped into three classes based on their cellular origin and antigenicity: α-interferon (leukocytes), β-interferon (fibroblasts) and γ-interferon (B cells). Recombinant forms of each group have been developed and are commercially available.
Due to their various biological activities, the use of interferons for treating a number of conditions has been proposed, including viral infections and various cancers. However, as with other proteins, use of interferons as pharmaceutical agents has generally been limited by several shortcomings, including antigenicity, which leads to formation of neutralizing antibodies and loss of clinical response, and a short half-life, which means that frequent doses are required to maintain therapeutically-effective concentrations of the protein.
These problems can be overcome by conjugating interferon to polymers, such as polyethylene glycol. However, while interferon-polymer conjugates are clinically beneficial, the widespread use of such conjugates in clinical practice requires formulations that can be stored for an extended period of time during manufacture and distribution to health care providers. Some interferon-polymer conjugates, however, rapidly deteriorate, even in frozen solutions. Lyophilization (also known as freeze-drying) is a process that can render an interferon-polymer conjugate in a form that can overcome this deficiency.
Lyophilization is a process whereby water is sublimed from a composition after it is frozen. In this process, pharmaceuticals and biologicals that are relatively unstable in an aqueous solution over a period of time can be placed into dosage containers in an easily processed liquid state, dried without the use of damaging heat and stored in a dried state for extended periods. A formulation designed for lyophilization often contains bulking ingredients that increase the amount of solid material, as well as cryoprotectants, lyoprotectants and other stabilizers to protect the active ingredient from damage during and after lyophilization.
U.S. Pat. No. 6,180,096 discloses that lyophilization of pegylated-interferon alpha conjugates may result in changes in the nature and degree of conjugation of PEG to interferon α. Such changes include degradation of the conjugate into free PEG and interferon α, subsequent attachment of the free PEG onto another pegylated-interferon molecule, or intramolecular shifts of PEG molecules from one site of conjugation to another within the same molecule. This patent discloses that the stability of pegylated-interferon alpha conjugates during and after lyophilization is achieved by lyophilizing such conjugates in a buffer, a stabilizer, a cryoprotectant and a solvent. While the '096 patent mentions several cryoprotectants could be used, including disaccharides, sucrose is the only cryoprotectant used in the only formulation that is specifically exemplified in this patent.
Lyophilized formulations containing Peginterferon alpha-2b, dibasic sodium phosphate anhydrous, monobasic sodium phosphate dihydrate, sucrose and polysorbate 80 are marketed by Schering Corporation, Kenilworth, N.J. as PEGINTRON™ vials and the PEGlNTRON™ REDIPEN®(Single-dose Delivery System) (See PEGINTRON™ Product Information, Rev. 2/05.). The REDIPEN® Single-dose Delivery System is a dual-chamber glass cartridge containing lyophilized peginterferon alfa-2b in one chamber and sterile water for injection in the other chamber. The manufacturer recommends room-temperature storage for PEGINTNTRON™ vials (i.e., 25° C.), and refrigerated storage for PEGINTRON™ REDIPEN® cartridges (i.e., 2° to 80° C.).
There is a present need for additional formulations that not only protect pegylated interferon conjugates from damage during and after lyophilization, but that also allow long-term storage at room temperature when lyophilized in glass cartridges. Ideally, such formulations should be amenable to a manufacturing process that is more cost-effective than the process used for sucrose-based formulations.